Melts destined for casting, more specifically, metal melts, give off much heat into their environment. In order to achieve good casting quality, an excessive cool-down during the casting process must be avoided. The casting in cold chamber die casting methods therefore takes place at a high speed and under a high pressure. Depending on the size of the cast part and its minimal wall thickness, the mold filling process of the die cast mold forming the mold cavity typically lasts a few milliseconds.
Each type of melt has certain suitable gate velocities and gating systems. Since a maximal gate velocity must not be exceeded, the cross-section of the gate surface and thus the part of the gating system that allows for separation of the sprue part from the die casting mold after the casting process must have sufficiently large dimensions. For planar and thin-walled cast parts, this requirement leads to a great proportion of circulating material, the mass of which can lie in the range of the mass of the cast part itself. The circulating material is subsequently melted again, which requires a considerable supply of external energy.
It is additionally necessary to provide that the melt does not solidify anywhere in the system through which the melt passes during the entire filling process. This can be provided by sufficiently large cross-sections of the gate channels. Large gate channels, however, lead to an increase of the casting mass so that a greater part of the melt is lost. As a rule, large cast parts with several gate areas or particularly thin-walled cast parts therefore require several gate channels as runners in order to avoid solidification in the mold cavity before it is completely filled.
In order to reduce the amount of circulating material, EP 1 201 335 B1 describes a hot chamber die casting method with a fan or tangential gate as a gating system. This gating system can uniformly fill the mold cavity, but leads to a complex structure of the casting device and requires an individual heating of the plurality of runners, more specifically, when using multi-cavity molds. The thin-walled runners are continuously heated during the cool-down of the cast part, which requires a considerable supply of energy, particularly for a gating systems with many branches required for large-scale parts.